CONTINUOUSWAVE

Hi there. I am new on the forum. I just registered after 20 years of really interesting readings of this forum.

I am considering buying a Boston Whaler boat in France. I understand that it is a 1986 25 REVENGE Walkaround Whaler Drive.



[Based on Figure 1] is the engine bracket an OEM Whaler Drive?

What will be the performance of the boat with the Yamaha 300-HP V6 engine?

Does this boat need flaps [trim tabs]?

Is an auxiliary engine needed?

Thanks for your kind consideration of my questions as a newbie.

In the 1986 Boston Whaler catalogue the boat is called a REVENGE 25 FULL CABIN. It is also called a REVENGE 25 Walkaround in some other literature. The boat was available with three power options: outboard engines with a notched transom; Sea Drive engines with a full transom, or; sterndrive engine with a full transom. There was no option listed for a Whaler Drive.

The engine bracket shown in Figure 1 does not look like an OEM Whaler Drive engine bracket. Typically a Whaler Drive will have a much larger buoyancy box that extends the full width of the bracket. The bracket in Figure 1 only has a buoyancy box in the center portion of the engine bracket. The bracket may be aluminum. A Whaler Drive would be of molded fiberglass construction.

The boat may have been originally built for Sea Drive engines, which could have been replaced with a non-OEM engine bracket and an outboard engine, as shown. This history for the boat is the most likely.

If the boat were originally built for outboard engines it would have had a notched transom. If that were the case, then the full transom conversion was done after the boat left the factory.

The boat was rated for maximum horsepower of 300-HP.

The top speed of the boat will have to be estimated based on total weight, power, and hull type.

I estimate as the weight as follows:

• the bare hull weight of the outboard model was 4,000-lbs
• add 250-lbs for the full transom
• add 250-lbs for the engine bracket
• add 1,000-lbs for fuel, crew, gear, etc.
• [oops--forgot engine, add 600-lbs]

The total boat weight will then be about [6,100-lbs].

The power is assumed to be 300-HP at the propeller shaft from the Yamaha F300 engine.

The hull factor or hull constant is assumed to be 180, based on my experience with this method and the classic Boston Whaler moderate V-hull or OUTRAGE hull design.

With these data and using the Crouch method, the top speed is calculated:

LBS = [6,100]
HP = 300
HULL CONSTANT = 180

and the calculated speed is [40-MPH]

[Revised for new total weight 6,100-lbs]

While the boat shown is not technically a "whaler drive" (WD) model, it could have been when originally manufactured. At some point an owner replaced the WD with an Armstrong brand bracket. Armstrong is an American company specializing in brackets and is well respected then and now.

It appears the installation of the Armstrong bracket is well done so it should not be seen as a negative when assessing the boat.

BreizhKerd wrote:Does this boat need flaps [trim tabs]?

There are many Boston Whaler moderate V-hull classic boats in the 25-foot length range that do not employ trim tabs. Generally engine trim will give good control of the bow rise. Side to side or listing can be corrected with trim tabs. These classic moderate V-hull boats tend to lean into the wind when on plane. I have found that moving crew weight in the boat to center or one side often corrects any list when underway on plane. My boat 22-foot and Whaler Drive single 225-HP engine boat does not have trim tabs.

With a powerful 300-HP single engine, propeller torque may induce a list. The 25-foot hull has a greater dead rise angle by a degree or two more than the 22-foot hull, and the 25-foot hull may be more prone to listing.

Phil T wrote:...the boat... could have been [a Whaler Drive model] when originally manufactured. At some point an owner replaced the WD with an Armstrong brand bracket.

I don't see a basis to infer that the boat originally had a Whaler Drive, as that option is not listed in the 1986 Boston Whaler Catalogue. In the catalogue there are three outline drawings of the boat as seen from above: Outboard, Sea Drive, Stern Drive.

In the more detailed 1986 Options and Price list, on page 43 for the 25 REVENGE WALK-AROUND CABIN, the Engine Option list notes:

Beyond the standard outboard model, this boat is also available in Stern Drive or Sea Drive power. Stern drive models use MERCRUISER 260...Sea Drive models include OMC SEA DRIVE twin 1.6 litre or single OMC SEA DRIVE 2.6 litre with VRO. Sea Drive models also add a 43-gallon removable fish well and hydraulic steering.

Other options listed are for "I/O" blank (for customer or dealer installation of a sterndrive engine) or SEA DRIVE blank (with a full transom and no further bracket of any kind), or a GIL BRACKET "for Sea Drive Blank only (Dual installation).

The base price for the REVENGE 25 WALK-AROUND CABIN or 25 REVENGE FULL CABIN in 1986 was $28,790. The SEA DRIVE blank price was $29,750--an additional $960 to fabricate the hull with a full transom.

The only other option for a full transom boat was the Stern Drive, but a Stern Drive boat would have a modification for mounting the inboard engine and an engine box in the cockpit.

I do not believe there are any remaining OMC SEA DRIVE engines actually attached to the transom of a Boston Whaler boat. On that basis I think the most reasonable inference about the history of this boat is that it came as a SEA DRIVE boat.

If the Boston Whaler hull stencil number or the federal Hull Identification Number can be located, the by contacting Boston Whaler customer service the actual configuration of the original boat may be possible to confirm.

Also, I am not aware of any actual Boston Whaler boat that was manufactured with a Whaler Drive having had the Whaler Drive removed and replaced with some other after-market bracket. I can't recall anyone even mentioning that as a possibility. People who own boats with the Whaler Drive option tend to be quite fond of the Whaler Drive. The only person I know that tends to disparage the Whaler Drive has never owned a Whaler Drive boat and thus has never removed a Whaler Drive, even though he seems very confident that a Whaler Drive was a speed reducing device and eschewed their use.

ASIDE: there is another 1986 Boston Whaler boat currently listed for sale in MARKETPLACE, a 27-footer that was originally sold with GIL brackets. See

viewtopic.php?f=5&t=6061#p35487

That 27-footer retained the GIL brackets and mounted more modern engines. I thought the coincidence in year of production was significant; it is another 1986 larger Boston Whaler boat with a full transom but no Whaler Drive.

Perhaps the REVENGE 25 under discussion here might have been ordered as a full-transom boat with the Gil Bracket option. Removal of one or two Gil Brackets would much simpler and more likely that removal of a Whaler Drive. The Gil Bracket was made with tubular members and provided no buoyancy box to compensate for the engine weight.


Fig. 2. A Gil bracket, seen more clearly in this illustration with a non-Boston Whaler boat.

Very big thank you to both of you Phil and Jim.


I have found some explanations and pictures about replacing a [OMC Sea Drive] by a Armstrong bracket on a 27FC [on some other website.] and that boat seems to be the same technical case as this boat.

I will ask the identification number to the seller or ask for the boat notice, and then make a reply in this post.

I am really impressed by your science and knowledge in this field.

Hope the boat will be rhe good boat, if not I will wait for the next one/

Jim--you said it was not possible to book [order] a [WhalerDrive] on a Revenge 25 in 1986. I was thinking about these specs (and of course now I understand it is not a [Whaler Drive as there is] the name Armstrong written on the side of the bracket) because i have read [about "it"] in the whaler/reference section of the continuous wave website. Is [there a mistake in the REFERENCE section]?

Others pictures here to continue the investigation.

Again a big thank you to both of you, and to this useful website.

Some pictures of the Yamaha F300 and the cockpit

The Whaler Drive option may have been available on the REVENGE 25 Walk-Through model.

The REVENGE 25 Walk-Through is a different model than the boat under discussion, which is the REVENGE 25 FULL CABIN and also sometimes called in Boston Whaler literature the REVENGE 25 Walkaround Cabin.

The aft cockpit bulkhead as shown in Figure 4 looks a bit unusual to me. Compare how that bulkhead appears with the bulkhead on an OUTRAGE 25 that was ordered as a Stern Drive Blank which appears below as Figure 5.


Fig. 5. The cockpit aft bulkhead on a 25-foot OUTRAGE that was ordered as a Sea Drive Blank. Note how the cockpit aft bulkhead differs significantly from the one seen above in Figure 4.


Fig. 6. Another view of the aft cockpit bulkhead on a 25-foot OUTRAGE that was ordered as a Sea Drive Blank. Note how the cockpit aft bulkhead differs significantly from the one seen above in Figure 4. There is no missing center section as seen in FIgure 4.

I am now wondering if the boat under discussion might have originally been made as a stern drive model because of the cut out in the aft cockpit bulkhead that seems to correspond to where the cockpit engine box would have been on a stern drive model.

Also, regarding the Whaler Drive, I don't see the Whaler Drive offered as an option until 1988. In 1987 Boston Whaler introduced a new model, the TEMPTATION, and those boats had a Whaler Drive. But the option for a Whaler Drive on OUTRAGE or REVENGE boats did not appear in the catalogue until 1988. This is another influence on why I very much doubt that the 1986 REVENGE 25 FULL CABIN boat under discussion could have been made in 1986 with a Whaler Drive.

BreizhKerd wrote:Very big thank you to both of you Phil and Jim.

But we have very different opinions about the boat's original construction. I hope you realize that.

After negotiations, I am going to visit the owner and test the boat on April 2, 2021.


The owner kindly gave me a few days ago the answer about which model it was, before the Armstrong Bracket.
Look at the pictures, it seems two SEA DRIVE engines were on the boat before this new bracket. And the winner is SEA DRIVE mounts.


Thank you again for your kind explanations and the given time.

I will have one or two test hours, and the boat will be inspected using cranage at the pier.

If some of you have important points to check, considering outboard AND boat, any specific matter on this boat ?

It will be very useful for me to go with a list of good questions.

Check all the through hull drain tubes. The originals were brass with rubber O rings.